Why does fungibility matter (and where did it go)?

Our ability to substitute with alternative sources of energy is a factor of how fungible energy really is–how easily we can bring alternative B to replace lost supply of energy A. This article discusses how the real world tends to intrude on fungibility of our various sources of energy and what this matters.

Economics – Oct 26

Heinberg: A back-row seat at the collapse revue
Oil, house prices, credit? 3 parts of the same story
Oil prices – a little more of the story
Many world stock markets now off 50% or more from peaks